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Finding the Fourth Proportional to 257.09, 385.63 and 86.21

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Solution

The fourth proportional to 257.09, 385.63 and 86.21 is: 129.31

Step by Step Solution

  1. Step 1: Write the proportion equation
    257.09 : 385.63 = 86.21 : x
  2. Step 2: Convert to fraction form
    257.09/385.63 = 86.21/x
  3. Step 3: Cross multiply
    257.09x = 385.63 × 86.21
  4. Step 4: Simplify right side
    257.09x = 33,243.02
  5. Step 5: Solve for x
    x = 33,243.02/257.09
  6. Step 6: Final answer
    x = 129.31

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.